In recent years, in order to improve an exhaust gas purification performance of a motor vehicle driving engine, the driving engine is being changed from an engine of a type providing an exhaust port of an exhaust gas in front of the vehicle to an engine of a type providing the exhaust port of the exhaust gas at the rear of the vehicle. For that reason, a heat is exhausted from an exhaust pipe of the engine at the rear side of the engine in an engine room in the vehicle direction, and the exhaust gas may cause a trouble to occur in equipment in the engine room. As a countermeasure, there is a desire to improve an air flow in the engine room, and improve a cooling performance in the engine room.
Up to now, there is a hot-wire anemometer using a hot wire (for example, refer to Patent Literature 1).